Integrated semiconductor laser array apparatus

Abstract

An integrated semiconductor laser array apparatus which is simple in structure and yet capable of stabilizing the light output from each individual semiconductor laser element. The integrated semiconductor laser array apparatus includes a semiconductor laser array provided by integrating a plurality of semiconductor laser elements. The semiconductor laser array includes a master semiconductor laser element selected from the plurality of semiconductor laser elements and slave semiconductor laser elements constituted of the remaining semiconductor laser elements. A laser beam output from the master semiconductor laser element is sensed by a photodiode and thereby a photocurrent corresponding to the received light ,intensity is generated and the bias current for the master semiconductor laser element is controlled by a first bias current control circuit such that the generated photocurrent is kept constant. The bias current for each of the slave semiconductor laser elements is controlled by a second bias current control circuit depending on the output from the First bias current control circuit such that the ratio between the bias current for the master semiconductor laser element, and the bias current for each of the plurality of slave semiconductor laser elements is kept constant.

What is claimed is: 
     
       1. An integrated semiconductor laser array apparatus comprising: a semiconductor laser array constructed by integrating a plurality of semiconductor laser elements, said semiconductor laser array including a master semiconductor laser element selected from said plurality of semiconductor laser elements and at least one slave semiconductor laser element constituted of the rest of the semiconductor laser elements;   a plurality of drive means for driving their respective semiconductor laser elements with a drive current composed of a bias current and a modulation current pulse;   a photodetector for sensing at least a portion of the laser beam emitted from said master semiconductor laser element to produce a photocurrent corresponding to the received light intensity;   first driving current control means for controlling a driving current for said master semiconductor laser element such that said photocurrent becomes constant; and   second driving current control means for controlling a driving current for said slave semiconductor laser element by following the control of the driving current for said master semiconductor laser element, wherein said first driving current control means comprises a current-to-voltage converter for converting said photocurrent into a voltage signal, a reference power supply for generating a reference voltage, a comparator for comparing said voltage signal with said reference voltage to output a signal at a level corresponding to the difference between the voltages, and first bias current control means for controlling the bias current for said master semiconductor laser element such that the output level of said comparator becomes a predetermined level, and said second driving current control means comprises second bias current control means for controlling the bias current for said slave semiconductor laser element such that the ratio between the bias current for said master semiconductor laser element and the bias current for said slave semiconductor laser element becomes constant.   
     
     
       2. An integrated semiconductor laser array apparatus according to claim 1, wherein said semiconductor laser array includes a plurality of slave semiconductor laser elements, and wherein said second bias current control means controls the bias current for each of said slave semiconductor laser elements such that the ratio between the bias current for said master semiconductor laser element and the bias current for each of said slave semiconductor laser elements becomes constant. 
     
     
       3. An integrated semiconductor laser array apparatus according to claim 2, wherein said ratio between the bias current for said master semiconductor laser element and the bias current for said slave semiconductor laser element is set to be varying for each of said slave semiconductor laser elements according to the temperature distribution on said semiconductor laser array. 
     
     
       4. An integrated semiconductor laser array apparatus according to claim 1, wherein the amplitude of said modulation current pulse is set up for each of said plurality of semiconductor laser elements according to the differential quantum efficiency of each of the elements. 
     
     
       5. An integrated semiconductor laser array apparatus according to claim 1, further comprising control means for controlling said modulation current pulse such that the amplitude thereof increases according to the temperature increase of said semiconductor laser element.